<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1{
            width: 100px;
            height: 200px;
            background: red;
            /* 元素溢出 */
            overflow: auto;
        }

        .box2{
            width: 50px;
            height: 300px;
            background: yellow;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box2">hello</div>
    </div>
</body>
</html>